I too prefer mono for lighter shooting heads. Of the monos I prefer oval, solid, running lines. Of the oval, solid running lines that I have tried I prefer the Guideline Compline, not too stretchy, yet retains very little memory, handles very nice. I would use the 35# test for a 570 grain weight. At about 600 grain I switch to 50# to stabilize the head better.

400gr is kind of the upper limit in my mind for mono. If you're going to be throwing at distance, mono sucks for mending the head anywhere outside 20'. The airflo ridge is the best runningline I've used but I use 40lb berkley big game on my small switch rod. Cheap and great.

PGK - I also am a fan of the Berkeley Big Game but do disagree with your comment about mending beyond 20 feet - I don't have any serious mending problems even at distance - I can pick up and mend pretty much to the fly line with not much problem - when going for distance (depending on your definition) I am often using a longer rod so mending again is not an issue. I use 40# Big Game with my Scott 1509 equipped with the RIO Flight 750 and it works very well out to long distances

This info is from Bob Meiser's site: "ELF level running lines: Level running lines are ideal for those situations where achieving maximum distance is the priority.

Our level running lines are available in three diameters. We recommend that you use the smaller diameters (.026 and .032) for lighter/shorter heads and smaller game fish, or for extreme distance deliveries. We suggest the heavier (.038) running lines to be used for larger heads and heavier game fish."

I really liked the E.L.F. lines but recently switched over to it's cousin the MendMaster (also sold by Meiser and made by Steve). Same construction with a bit more belly and more mendable. I felt that I could cast a fly with the E.L.F. farther than I could fish it, and I'm not the most amazing spey caster.

450 sounds like a light tip rod. If you are going to fish some heavier tips, annything that gets down 4 plus ft in medium fast current the old Airflow miricle braid is awesome, I am not sure if the new stuff is the same, it's back ordered right now. For dry lines a floating mono is fine.

IMO the best running line which shoots the easist, doesn't stick to you hands and is easy to manage is Guideline comp line. However, you must straighten it out initially. When I say straighten I mean run you fingers down the line with pressure until you fingers nearly start to burn. Once you do this it will stay straight if you fish a decent amount. If it sits on a reel for a longer period of time you will have to straighten it again. Kinda expensive though.